Using an electrical meter safely and efficiently is perhaps the most valuable skill an electronics technician can master, both for the sake of their own personal safety and for proficiency at their trade. It can be daunting at first to use a meter, knowing that you are connecting it to live circuits that may harbor life-threatening levels of voltage and current.

This concern is not unfounded, and it is always best to proceed cautiously when using meters. Carelessness more than any other factor is what causes experienced technicians to have electrical accidents.

Multimeters

The most common piece of electrical test equipment is a meter called the multimeter. Multimeters are so named because they have the ability to measure multiple variables: voltage, current, resistance, and often many others, some of which cannot be explained here due to their complexity.

In the hands of a trained technician, the multimeter is both an efficient work tool and a safety device. In the hands of someone ignorant and/or careless, however, the multimeter may become a source of danger when connected to a “live” circuit.

There are many different brands of multimeters, with multiple models made by each manufacturer sporting different sets of features. The multimeter shown here in the following illustrations is a “generic” design, not specific to any manufacturer, but general enough to teach the basic principles of use:

You will notice that the display of this meter is of the “digital” type: showing numerical values using four digits in a manner similar to a digital clock. The rotary selector switch (now set in the Off position) has five different measurement positions it can be set in: two “V” settings, two “A” settings, and one set in the middle with a funny-looking “horseshoe” symbol on it representing “resistance.”

The “horseshoe” symbol is the Greek letter “Omega” (Ω), which is the common symbol for the electrical unit of ohms.

Of the two “V” settings and two “A” settings, you will notice that each pair is divided into unique markers with either a pair of horizontal lines (one solid, one dashed) or a dashed line with a squiggly curve over it. The parallel lines represent “DC” while the squiggly curve represents “AC.” The “V” of course stands for “voltage” while the “A” stands for “amperage” (current).

The meter uses different techniques, internally, to measure DC than it uses to measure AC, and so it requires the user to select which type of voltage (V) or current (A) is to be measured. Although we haven’t discussed alternating current (AC) in any technical detail, this distinction in meter settings is an important one to bear in mind.

Multimeter Sockets

There are three different sockets on the multimeter face into which we can plug our test leads. Test leads are nothing more than specially-prepared wires used to connect the meter to the circuit under test.

The wires are coated in a color-coded (either black or red) flexible insulation to prevent the user’s hands from contacting the bare conductors, and the tips of the probes are sharp, stiff pieces of wire:

The black test lead always plugs into the black socket on the multimeter: the one marked “COM” for “common.” The red test leads plugs into either the red socket marked for voltage and resistance or the red socket marked for current, depending on which quantity you intend to measure with the multimeter.

To see how this works, let’s look at a couple of examples showing the meter in use. First, we’ll set up the meter to measure DC voltage from a battery:

Note that the two test leads are plugged into the appropriate sockets on the meter for voltage, and the selector switch has been set for DC “V”. Now, we’ll take a look at an example of using the multimeter to measure AC voltage from a household electrical power receptacle (wall socket):

The only difference in the setup of the meter is the placement of the selector switch: it is now turned to AC “V”. Since we’re still measuring voltage, the test leads will remain plugged in the same sockets.

In both of these examples, it is imperative that you not let the probe tips come in contact with one another while they are both in contact with their respective points on the circuit. If this happens, a short-circuit will be formed, creating a spark and perhaps even a ball of flame if the voltage source is capable of supplying enough current! The following image illustrates the potential for hazard:

This is just one of the ways that a meter can become a source of the hazard if used improperly.

Voltage measurement is perhaps the most common function a multimeter is used for. It is certainly the primary measurement taken for safety purposes (part of the lock-out/tag-out procedure), and it should be well understood by the operator of the meter.

Being that voltage is always relative between two points, the meter must be firmly connected to two points in a circuit before it will provide a reliable measurement. That usually means both probes must be grasped by the user’s hands and held against the proper contact points of a voltage source or circuit while measuring.

Because a hand-to-hand shock current path is the most dangerous, holding the meter probes on two points in a high-voltage circuit in this manner is always a potential hazard. If the protective insulation on the probes is worn or cracked, it is possible for the user’s fingers to come into contact with the probe conductors during the time of test, causing a bad shock to occur. If it is possible to use only one hand to grasp the probes, that is a safer option.

Sometimes it is possible to “latch” one probe tip onto the circuit test point so that it can be let go of and the other probe set in place, using only one hand. Special probe tip accessories such as spring clips can be attached to help facilitate this.

Remember that meter test leads are part of the whole equipment package and that they should be treated with the same care and respect that the meter itself is. If you need a special accessory for your test leads, such as a spring clip or other special probe tip, consult the product catalog of the meter manufacturer or other test equipment manufacturer.

Do not try to be creative and make your own test probes, as you may end up placing yourself in danger the next time you use them on a live circuit.

Also, it must be remembered that digital multimeters usually do a good job of discriminating between AC and DC measurements, as they are set for one or the other when checking for voltage or current.

As we have seen earlier, both AC and DC voltages and currents can be deadly, so when using a multimeter as a safety check device you should always check for the presence of both AC and DC, even if you’re not expecting to find both! Also, when checking for the presence of hazardous voltage, you should be sure to check all pairs of points in question.

For example, suppose that you opened up an electrical wiring cabinet to find three large conductors supplying AC power to a load. The circuit breaker feeding these wires (supposedly) has been shut off, locked, and tagged. You double-checked the absence of power by pressing the Start button for the load. Nothing happened, so now you move on to the third phase of your safety check:

First, you check your meter on a known source of voltage to see that it’s working properly. Any nearby power receptacle should provide a convenient source of AC voltage for a test. You do so and find that the meter indicates as it should. Next, you need to check for voltage among these three wires in the cabinet. But voltage is measured between two points, so where do you check?

The answer is to check between all combinations of those three points. As you can see, the points are labeled “A”, “B”, and “C” in the illustration, so you would need to take your multimeter (set in the voltmeter mode) and check between points A & B, B & C, and A & C.

If you find voltage between any of those pairs, the circuit is not in a Zero Energy State. But wait! Remember that a multimeter will not register DC voltage when it’s in the AC voltage mode and vice versa, so you need to check those three pairs of points in each mode for a total of six voltage checks in order to be complete!

However, even with all that checking, we still haven’t covered all possibilities yet. Remember that hazardous voltage can appear between a single wire and ground (in this case, the metal frame of the cabinet would be a good ground reference point) in a power system.

So, to be perfectly safe, we not only have to check between A & B, B & C, and A & C (in both AC and DC modes), but we also have to check between A & ground, B & ground, and C & ground (in both AC and DC modes)! This makes for a grand total of twelve voltage checks for this seemingly simple scenario of only three wires. Then, of course, after we’ve completed all these checks, we need to take our multimeter and re-test it against a known source of voltage such as a power receptacle to ensure that it’s still in good working order.

Using a Multimeter to Check For Resistance

Using a multimeter to check for resistance is a much simpler task. The test leads will be kept plugged in the same sockets as for the voltage checks, but the selector switch will need to be turned until it points to the “horseshoe” resistance symbol. Touching the probes across the device whose resistance is to be measured, the meter should properly display the resistance in ohms:

One very important thing to remember about measuring resistance is that it must only be done on de-energized components! When the meter is in “resistance” mode, it uses a small internal battery to generate a tiny current through the component to be measured.

By sensing how difficult it is to move this current through the component, the resistance of that component can be determined and displayed. If there is an additional source of voltage in the meter-lead-component-lead-meter loop to either aid or oppose the resistance-measuring current produced by the meter, faulty readings will result. In a worse-case situation, the meter may even be damaged by the external voltage.

The “Resistance” Mode Of A Multimeter

The “resistance” mode of a multimeter is very useful in determining wire continuity as well as making precise measurements of resistance. When there is a good, solid connection between the probe tips (simulated by touching them together), the meter shows almost zero Ω. If the test leads had no resistance in them, it would read exactly zero:

If the leads are not in contact with each other or touching opposite ends of a broken wire, the meter will indicate infinite resistance (usually by displaying dashed lines or the abbreviation “O.L.” which stands for “open loop”)

Measuring Current with a Multimeter

By far the most hazardous and complex application of the multimeter is in the measurement of current. The reason for this is quite simple: in order for the meter to measure current, the current to be measured must be forced to go through the meter.

This means that the meter must be made part of the current path of the circuit rather than just be connected off to the side somewhere as is the case when measuring voltage. In order to make the meter part of the current path of the circuit, the original circuit must be “broken” and the meter connected across the two points of the open break. To set the meter up for this, the selector switch must point to either AC or DC “A” and the red test lead must be plugged in the red socket marked “A”.

The following illustration shows a meter all ready to measure current and a circuit to be tested:

Now, the circuit is broken in preparation for the meter to be connected:

 

The next step is to insert the meter in-line with the circuit by connecting the two probe tips to the broken ends of the circuit, the black probe to the negative (-) terminal of the 9-volt battery, and the red probe to the loose wire end leading to the lamp:

This example shows a very safe circuit to work with. 9 volts hardly constitutes a shock hazard, and so there is little to fear in breaking this circuit open (barehanded, no less!) and connecting the meter in-line with the flow of current. However, with higher power circuits, this could be a hazardous endeavor indeed.

Even if the circuit voltage was low, the normal current could be high enough that an injurious spark would result at the moment the last meter probe connection was established.

Another potential hazard of using a multimeter in its current-measuring (“ammeter”) mode is the failure to properly put it back into a voltage-measuring configuration before measuring the voltage with it. The reasons for this are specific to ammeter design and operation. When measuring circuit current by placing the meter directly in the path of the current, it is best to have the meter offer little or no resistance to current flow.

Otherwise, the additional resistance will alter the circuit’s operation. Thus, the multimeter is designed to have practically zero ohms of resistance between the test probe tips when the red probe has been plugged into the red “A” (current-measuring) socket. In the voltage-measuring mode (red lead plugged into the red “V” socket), there are many mega-ohms of resistance between the test probe tips, because voltmeters are designed to have close to infinite resistance (so that they don’t draw any appreciable current from the circuit under test).

When switching a multimeter from current- to voltage-measuring mode, it’s easy to spin the selector switch from the “A” to the “V” position and forget to correspondingly switch the position of the red test lead plug from “A” to “V”. The result—if the meter is then connected across a source of substantial voltage—will be a short-circuit through the meter!

To help prevent this, most multimeters have a warning feature by which they beep if ever there’s a lead plugged in the “A” socket and the selector switch is set to “V”. As convenient as features like these are, though, they are still no substitute for clear thinking and caution when using a multimeter.

 

All good-quality multimeters contain fuses inside that are engineered to “blow” in the event of excessive current through them, such as in the case illustrated in the last image. Like all overcurrent protection devices, these fuses are primarily designed to protect the equipment (in this case, the meter itself) from excessive damage, and only secondarily to protect the user from harm.

A multimeter can be used to check its own current fuse by setting the selector switch to the resistance position and creating a connection between the two red sockets like this.

 

A good fuse will indicate very little resistance while a blown fuse will always show “O.L.” (or whatever indication that model of multimeter uses to indicate no continuity). The actual number of ohms displayed for a good fuse is of little consequence, so long as its an arbitrarily low figure.

So now that we’ve seen how to use a multimeter to measure voltage, resistance, and current, what more is there to know? Plenty! The value and capabilities of this versatile test instrument will become more evident as you gain skill and familiarity using it.

There is no substitute for regular practice with complex instruments such as these, so feel free to experiment on safe, battery-powered circuits.

source:https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-meter-usage/

See more:

Why You Should Have a Multimeter When Doing Any Electrical Work

Throwing darts is a fascinating sport to play at a pub or even at home. You can play darts against your friends for entertainment. It requires basic assistants such as a good throwing stance and grippy darts to throw successfully. Also, it demands certain skills and tips to be an expert in this sport.

How to throw darts like a pro? Keep track of our post as you will become a master of throwing darts after finishing reading it. Are you ready? Let’s go!

 

5 Simple Tips To Throw Darts Like A Pro

Tip #1: Be really comfortable with outer factors

As for the dart, make sure you don’t have a firm grip but a nice grip that creates a comfortable feeling with your playing style. Also, a well-balanced stance is a must. You don’t want a wobbly stance to destroy your performance, do you? Besides, another important outer factor is that you must come to terms with cheers, laughs, or provoking words to chill yourself out and focus on the game.

 

Tip #2: Control your body

Stand balanced and don’t lean too far forward. One foot forward the other is enough. The hand which you are holding the dart must be close to your body or you’ll lose control of it and generate flop shots. When throwing the darts, you need to keep your arm as still as possible. So far, we’ve mentioned your feet, hand, and arm but the top trick is revealed yet on our third trip.

Related: Are You Looking For A Good Bristle Dartboard? Let’s Take A Look In This Article! 

 

Tip #3: The secret lies in your arm posture

Firstly, you have to bring your arm down in front and line things up with your elbow at 90 degrees. The usual pitch is placing your elbow below your chin. We see our target between our thumb and index finger which is called the sightline. Keeping everything in line and releasing with your power-this is when the magic happens. The more shots you throw, the nearer your darts are to the central point of the circles.

 

Tip #4: Be in charge of your wrist

Most people don’t buy it but the trick of throwing a basketball into the net and throwing darts right at the dartboard is much more related than you think. They all demand huge strengths from your wrists and precise direction. Warming up your wrist joint first by rotating it around will provide better flexibility and firmness.

On the other hand, remember to shoot off the darts about half of the circle. Don’t go all the way from turning your hand upward to downward. This is quite complicated to visualize. Just imagine that instead of doing a full circle dunk with your hand, you only do half of it.

 

Tip #5: You gotta have fun with what you are doing

If you don’t enjoy the game, you’re gonna continually be distracted and frustrated, and that’s not leading to success. Be balanced on the toll line and try to find a nice start that you feel comfortable with to practice more and more. As the 20-hour rule to learn something new, you will feel stupid and disorientated at first but will improve much over time and gain confidence as well as urges to perform in front of a local bar with loads of people.

 

In conclusion

We bet this article is obviously a game-changer for dart throwers. These 5 tips to throw darts as a pro comes in handy not only for newbies but also for professional players. The basic requirements are a good balanced stance, a nice comfy dart, and some little tricks with your elbows and wrists.

The next time you want to show off your skills at the bar, don’t forget to apply these tips and impress others. Also, share this article with your pals as well because it’s an old saying that the more the merrier!

You may also like: Freestanding Dartboards That Will Not Damage Your Wall – Which Is The Best?

Gone are the days when 3D art was solely a reserve for large corporations. No average person would have a 3D printer in his living room. Times have however changed and 3D printing tools are growing more affordable with every dawn of a new day.

Even more affordable are the 3D pens which have since infiltrated the market. You may want to have a look at the best in the market as detailed in this piece by Rabbit Reviews. 

What is the cost of 3D pens?

A random search on Amazon yields the following results:

• SCRIB3D P1 3D printing pen with display – $29
• MYNT3D professional printing 3D pen with OLED display – $ 59
• SCRIB3D advanced 3D printing pen with display – $49
• 3Doodler Create+ 3D printing pen – $78
• 3Doodler Start Essentials 3D pen set for kids – $ 48
• Tech 4 Kids 3D Magic Imagi Pen – $19
• Wacom Pro Pen 3D – $83
• MYNT3D Junior 3D pen for kids – $34

In a very general sense, you can get a high end 3D pen with less than $ 100. Still, with less than 50 bucks, you can get yourself a good quality budget-friendly 3D pen. On the extreme end, you can still get a 3D pen with less than 20 bucks. Remember to factor in the costs of the filament and 3D pen mats. 

Are 3D pens worth it?

Having tasted the benefits of using 3D pens, I personally wouldn’t take a second thought if I were asked to rethink my investment decision.  Nowadays, I literally think in 3D. If I have to illustrate some object or concept, I do it in 3D. And that’s the beauty of 3D pens. 

They quickly breathe life into an otherwise boring class or brainstorming session. I guess people are so used to ink on paper that it no longer strikes a chord. Try 3D and you will likewise confess that 3D pens are worth it.  

What is the cheapest 3D pen?

I recently spotted a 3D pen by the name Dewang going for 3.83 USD. Quite incredible! Another one named Lihuachen retails for about 15 bucks. Of course, these are Chinese made – you might have guessed. And I’ve come to conclude that there is no price limit below which a product can’t be priced. You would be surprised to find other brands priced at less than $3 – who knows! But it all depends on what you are looking for in the 3D pen. My favorite is the 3Doodler Create+ which cost me about 80 bucks. I’m simply a fan of reputable brands. It naturally gives me the confidence that I can never go wrong.

What is the best 3D pen for adults?

In this category, I proudly propose the AIO Printing Pen. Its most outstanding feature is the 5-speed setting – which adequately brings out the artist in you. One downside with this pen is the fact that you can only use PLA filaments. But that is no big deal given the versatility of PLA filaments. Spare some 60 or so bucks and enjoy its marvelous features.

Likechoosing Trump or Biden, multitudes of people are still divided on which filament is best for the job. And the push and pull is not yet about to end. That is because of the different personalities of different people. 

For instance, my sole preference is the PLA filament. ABS could still serve well in my art endeavours, but I never use it. I wouldn’t be surprised to learn that you only use ABS – nothing wrong about that. But in case you’re still hanging on the fence, I hope this brief discussion will open your eyes.

For a detailed sight into the best 3D pens in the market, read this piece on Reviews Rabbit.  

What’s the difference between ABS and PLA filament types for 3D pens

The ABS and PLA are the two most popular filaments for use with 3d pens. Of course, there are other filament materials – but we can reserve that for another day.

ABS is an abbreviation for Acrylonitrile Butadiene Styrene – you don’t have to remember that at all. What you need to understand is that it is an oil-based thermoplastic. This is the same material used in vehicles, and toys such as the popular LEGO. 

One distinct feature with ABS is the odour it lets off as it melts. It melts at around 225 – 2500 C. You therefore want to avoid it if you are allergic to such smells. On the positive side, ABS filaments yield objects with higher strength, durability, and flexibility than those created using PLA filaments. 

PLA is the short for Polylactic Acid. This is a biodegradable thermoplastic. It is largely plant based, with the chief ingredients coming from sugarcane, soy beans, and cornstarch. You will mostly find it in plastic cups and food packaging. 

PLA requires a slightly lower temperature to melt than the ABS – i.e about 180 – 2200 C. And its melting does not release unpleasant smells. Indeed, if you are sensitive enough, you can recognize some trace smell of honey.

What is better for 3D printing, PLA or ABS?

In regards to printing, the odorless nature of PLA makes it more child-friendly. Additionally, it is highly cohesive and thus can be used on surfaces such as metal, glass, and ceramic. Its low melting temperature supports a smooth flow of the molten plastic out of the nozzle. In other words, it becomes easy to draw with PLA filaments.

On the negative side, the low melting point of PLA makes the created objects vulnerable to heat degradation. Worse still, the objects start biodegrading within a year. It is therefore not suitable for objects set to last several years. 

ABS objects are harder than PLA objects. Also, they feature a somewhat glossy surface. ABS is resistant to several harsh chemicals. However, it easily dissolves in acetone – a property which can be advantageously used to glue different ABS parts together. 

Does PLA stick to ABS?

Sure, it does. As discussed above, PLA sticks to pretty any material. You can comfortably glue together PLA and ABS objects.

How strong is 3D pen filament?

To be exact, the tensile strength of ABS filament is around 47.7 MPa, while that of PLA is about 64.4 MPa. This implies that PLA has higher tensile strength than ABS – meaning you can considerably stretch PLA objects before snapping them. 

What is the strongest 3D filament?

Aside from ABS and PLA, the strongest 3D filament is the polycarbonate – not very popular but it is the king. Polycarbonate melts at 2900 C. this is way higher than the melting points of both ABS and PLA.

Camping is a great way for us to integrate into nature and improve many skills in life.

Here are 5 great benefits of camping:

1. Camping helps you improve your problem-solving ability

Sometimes, camping and outdoor activities present challenges that you cannot solve daily, but through where to camp, how to set up a tent, or how to cope with situations when You are not equipped with many tools for the camping trip, which will help you improve the ability to solve problems that occur in your life.

Moreover, camping also helps you to have new experiences and those experiences will help you to be more confident in life.

2. Good camping for educating children

Most parents know that camping takes children to a whole new natural world and requires them to have more skills to overcome new challenges. For example, if it rains when camping, exposure to a range of different challenges not only keeps a child’s brain healthy but also increases their chances of learning. Therefore, many parents believe camping has a positive impact on the education of children.

3. Camping helps you sleep better

Middle-aged and older people often have trouble sleeping at night. Therefore, another important reason is that camping is good for everyone. If you’re sleep-deprived and have trouble sleeping, camping can reset your body clock and help you sleep better, waking up early in the morning.

Normally we use artificial light in our daily life but the fact that camping can help us adjust to the natural light and dark cycle. For a long time, adequate sleep has been considered an important factor for human health, and camping helps family members minimize fatigue and grit.

4. Camping will help you increase your exercise